Project Publications

Related National Programs

1a.Objectives (from AD-416):
The overall goal of the proposed research is to identify foods, nutrients, and food components that promote health and prevent disease in at-risk populations; where possible diet-gene interactions will be explored. Over the next 5 years we will focus on the following objectives:

OBJECTIVE 1: Determine the effects of specific foods, fortified foods, and nutrients on bone health of at-risk population groups.
Sub-objective 1.A. Determine the effects of carbonated beverages and milk on calcium kinetics and calcium efflux from the skeleton of women and girls.
Sub-objective 1.B. Determine the effects of vitamin B12 deficiency on markers of calcium kinetics, bone health, and calcium metabolism in postmenopausal women.

OBJECTIVE 3. Investigate the effect of Zn supplementation on the development of prostate cancer, a cancer common in African-Americans, using a mouse prostate cancer model (TRAMP).

1b.Approach (from AD-416):
The overall goal is to identify foods, nutrients, and food components that promote health and prevent disease in at-risk populations and to identify diet gene interactions where possible. To achieve this goal, human studies will be conducted investigating the effects of carbonated beverages and milk on calcium kinetics and calcium efflux from the skeleton of women and girls; effects of vitamin B12 deficiency on markers of calcium kinetics, bone health, and calcium metabolism in postmenopausal women; and determine the absorption of 14C-vitamin B12 from fortified foods in elderly with gastric atrophy and H. pylori infection, pre- and post H. pylori treatment. Animal models will be used to investigate the impact of SNPs in a major Zn uptake gene (ZIP4) on dietary Zn absorption using ZIP4-expressing cell lines and to investigate the effect of Zn supplementation on the development of prostate cancer, common in African-American men. There is a need to devise effective nutrition interventions to prevent the progress of chronic disease in at-risk populations. Replacing: 5306-51520-006-00D (Van Loan, Allen) and 5306-51530-014-00D (Huang). Formerly 5306-51520-006-00D (4/09).

3.Progress Report:
Objective 1 included 2 human intervention studies using 41Ca isotope to track loss of calcium from the skeleton. In postmenopausal women consuming milk and yogurt vs. calcium and D supplements no difference was observed in the loss of calcium from the skeleton whether the calcium and D came from dairy foods or tablets. The second project examined changes in bone metabolism in women with insufficient B12. Data from this project suggests there was no benefit to bone metabolism when given B12 treatment. Objective 2a determine the absorption of 14C-vitamin B12 from fortified foods using the novel approach of administering vitamin B12 labeled with 14C, which can be followed in the body, using accelerator mass spectrometry. The labeled vitamin was added to flour, and made into bread rolls in the same way that B12 fortified flour would be used. Blood, urine and feces were collected from 5 healthy participants over the next 5 days and the 14C measured. About 60% of the 0.8 ug of B12 given to each subject was absorbed. We intended to study absorption in an additional 5 elderly with gastric atrophy, but after a major recruiting effort no volunteers met our criteria in this category. We are now recruiting elderly with reduced gastric acid due to taking proton pump inhibitors and have completed one such subject. The 14C-B12 was also injected into chickens to produce labeled eggs which were fed to 10 healthy volunteers. From excretion of 14C in feces and urine we found that 50% of the B12 was absorbed from eggs providing 1.4 ug B12, but only 20% from eggs providing 2.6 ug. An unexpected finding was that B12 not absorbed in the ileum appears to be degraded lower in the intestine, possibly by bacteria. Objective 2b was terminated due to lack of effect; no further work in this area has been conducted. Objective 3: was not initiated due to lack of funding for the animal feeding study. Instead, a project aiming to identify the molecule(s) that may underlie the aggressiveness of prostate cancer was conducted. The CD40 receptor, a signal protein for immune and inflammatory response located on the cell surfaces of T and B cells in the immune system, has been experimentally confirmed to interact with ZnT7 protein using fusion proteins purified from bacterial lysate. To examine whether CD40 and ZnT7 are also interacting with each other in mammalian cells, HA-tagged human CD40 cDNA was inserted into a mammalian expressing vector. The resulting plasmid was confirmed by PCR and DNA sequencing. HA-CD40 plasmid was then transfected into CHO cell lines with or without ZnT7 over-expression. Transfected cells were stained for CD40 intracellular localization or harvested for immunoprecipitation assay. Preliminary immunocytochemistry results suggest that over-expression of ZnT7 in mammalian cells may negatively regulate the abundance of CD 40 in mammalian cells.

4.Accomplishments
1.
Vitamin B12 is well absorbed from fortified flour and eggs but less is absorbed with higher doses. To measure the absorption of vitamin B12 from foods and fortified flour, ARS scientists at the Western Human Nutrition Research Center at Davis, California, used a novel approach to label vitamin B12 with extremely small amounts of the isotope 14C. The labeled vitamin added to flour resisted fermentation and baking and was well absorbed. The labeled vitamin was also given to chickens to produce labeled eggs which were fed to humans, and the vitamin was also well absorbed from eggs. However, the percent of the B12 absorbed was strongly inversely related to the amount of B12 fed, so just a small amount more of the vitamin would be absorbed from two eggs than from one egg. These findings show that vitamin B12 fortification of flour is an effective way of improving B12 status, but eating foods high in B12 is much less efficient.

2.
Zinc’s effect on immunity is discovered. Zinc transporter 7 (ZnT7) interacts with human CD40 (a signal protein involved in mediating immune and inflammatory responses that activate macrophage antigen presenting), T cell-dependent immunoglobulin class switching of B cells, resting B cell activation, and memory B cell development. It has been well known that dietary zinc deficiency affects immune function leading to frequent respiratory infections, pneumonia, and diarrhea. However, the underlying mechanism is not understood. ARS researchers at Davis, California, discovered that alteration of cytoplasmic zinc concentration through adjusting zinc transporter expression levels could have significant effects on the activity of the signaling pathway mediated by CDL/CD40 interaction. This finding is novel and it will greatly contribute to the fundamental knowledge of how zinc affects immune function. In addition, it will have an important impact on the development of diagnostic and prognostic biomarkers in monitoring immune function and inflammatory response in humans.